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Posted by Ken Maltby on April 25, 2008, 5:42 pm
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>
>> Air tools typically use a vane motor. Comprised of a cylindrical rotor,
>> with longitudinal
>> slots, mounted eccentrically within a slightly larger cylinder, In the
>> slots are vanes
>> made of light, stiff material, like phenolic resin board, and these vanes
>> are
>> spring-loaded so as to make contact with the inner surface of the outer
>> cylinder. As the
>> inner cylinder rotates, the volume of the spaces bounded by any pair of
>> vanes varies
>> smoothly with the rotational position of the inner drum w.r.t. the outer
>> ones. So an air
>> inlet is positioned at a point where the volume of such a space is small,
>> and an outlet
>> where the volume of such a space is large. Admit compressed air to the
>> inlet, and it
>> expands by causing the inner cylinder to rotate.
>
>> Such a motor would probably run on steam, for a while.
>
> I wonder if the heat and moisture would attack the resin board? Iwonder
> if proploged duty cycles would ruin the tool?
>
While that is a possibility, it's quite possible that there would
be no such problem, especially given the limited amount of live
steam from your pressure cooker boiler. Also, not all of these
air tools are built the same or use the same materials.
>
> Remember that they require a shot
>> of oil in the air inlet on a daily basis, if used daily. Even in
>> compressed-air service,
>> they usually don't run continuously. I doubt such a motor would run for
>> an extended period
>> on steam, or that it would be very efficient.
>
> Yeah - I see your point.
>
I don't. Short of some data, which isn't on hand, I can't see
how any claims could be made about the efficiency of air tools
running off steam pressure vice air pressure. It may be that the
same attachment that supplies oil to the compressed air line
would work for a steam line. Continuous duty versus intermittent
duty ratings have effect for factors that can build up/ get worse
over time; like heat effects an electric motor. (An electric motor
often goes from having a short duty cycle to continuous duty by
the simple addition of a fan on the output shaft.)
>> Autos back in the '70s and '80s used to use a "smog pump", a vane-type
>> air pump of similar
>> construction. They were intended for more or less continuous service,
>> albeit pumping
>> filtered air, and were driven off the engine via a V-belt. If you could
>> find one of those
>> that isn't seized up, it would be an ideal unit to experiment with.
>
> Cool. My dad is in the auto repair business. Likely he knows someone at
> a junk yard.
>
From what I've seen of them, on the net, it could be a better
way to go. You may have to restrict the exhaust to increase
the operating pressure, though, depending on the torque required
to turn your generator/motor and charge your batteries.
> --
> The whole problem with the world is that fools and fanatics are always so
> certain of themselves, but wiser people so full of doubts.
> -- Bertrand Russel
>
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